Synaptic transmission 2 Flashcards
What are the two types of neurotransmitters?
Small molecule - simple AA’s or AA-like compounds
Large molecule - Peptides
Where are small molecule neurotransmitters packaged?
Axon terminal
Proteins for synthesis are made in soma and sent to terminal
Where are large molecule neurotransmitters packaged?
Synthesized and packaged in the soma
Completely filled vesicle is transported to the axon terminal
What enzyme is responsible for ACh formation?
Acetylcholinetransferase
Located in axon terminal
What are the three catecholamines and what amino acid are they derived from?
Dopamine, Norepinephrine, epinephrine
Derived from tyrosine
What is the indoleamine and what amino acid is it derived from?
Serotonin
Tryptophan
What is the imidazoline and what amino acid is it derived from?
Histamine
Derived from histidine
What is the role of glycine?
Principle inhibitory neurotransmitter in the spinal cord
What is the role of glutamate?
Principle excitatory neurotransmitter in the central nervous system
What is the role of GABA?
Principle inhibitory neurotransmitter in the brain
How does ATP function as a neurotransmitter?
Released an then cleaved to form adenosine
Adenosine acts as a sleep signal
Describe nitric oxide as a neurotransmitter.
Membrane soluble gas
Synthesized directly in response to Ca influx, not stored in vesicles
Binds to cytosolic guanylyl cyclase in postsynaptic cells
What is co-expression?
Many neurons release 2 neurotransmitters
Typically one small and one peptide
What are the two types of neurotransmitter receptors?
Ionotropic - direct
Mtabotropic - indirect
What are four important ionotropic receptors?
Nicotinic ACh receptor
GABAa
AMPA
NMDA glutamate receptor
What is a postsynaptic potential?
Change in postsynaptic ion permeability caused by released neurotransmitter
What is an excitatory postsynaptic potential (EPSP)?
Postsynaptic repsonse which increases the probability that postsynaptic neuron will fire an action potential
Generally depolarizes
What is an inhibitory postsynaptic potential (IPSP)?
Postsynaptic response which decreases the probability that postsynaptic neuron will fire an action potential
May hyperpolarize
How can an increase in conductance cause an EPSP?
Opens an ionotropic cation channel
Permeable to both Na and K ions
Sometime also Ca
Describe the driving forces for Na and K at resting potential
Na is inward, K is outward
Na is many times larger than K driving force
What is the net current flow when the cation channel is open?
The net current flow is inward and the cell will depolarize
Due to Na driving force being larger than K
What is the amplitude of the EPSP dependent on?
The number of cation channels opened
How can a decrease in conductance cause an EPSP?
Closing ion channels that normally hyperpolarize the membrane
This removes the hyperpolarizing influence
What is an example of a receptor that causes an EPSP by decreasing conductance?
Muscarinic ACh receptor
M1, M3, M5
How can an IPSP be caused by an increase in conductance?
Indirectly gated K channels
Directly gated Cl channels
What is the mechanism for Indirectly K channels?
Receptor activated G protein
G-protein opens additional K channels in postsynaptic membrane
GABAb, M2 and M4 mAChRs
What does E(Cl) in order for the effect on the membrane to be inhibitory?
As long as E(Cl) is negative to threshold
E.g. GABAa, glycine receptor
How does the opening of directly gated chloride channels affect membrane potential?
Since E(Cl) and resting potential are very close, opening chloride channels stabilizes the membrane near the normal resting potential
How can an IPSP be caused by conductance decrease?
Postsynaptic neuron contains Na/K permeable leak channels that are open in the resting membrane
Metabotropic receptor closes these channels, removing a depolarizing influence
Only happens at a specialized class of synapse in the reina
